Minimally processed tomato using a simple developed filtration device, common salt and vegetable oil can preserve tomato concentrate

Abstract

In attempt to produce and preserve tomato concentrate, without destroying some useful nutrients, in a rural area where there is no electricity, a minimal processing method is necessary. In this study, a simple filtration unit was developed. Fresh tomatoes (Solanum lycopersicum) (3.50 kg) were bought, cleaned and blended. Initial moisture content (MC) of the slurry (3.0 g) was determined and 3.0 kg slurry filtered. The amounts of concentrate, filtrate and filtration period were noted. Initial MC of the concentrate was also found. A mixture of concentrate (200 g), vegetable oil (30 ml) and salt (12.0 g) was prepared for preservation as sample A. This was re-prepared but with 10.0 and 8.0 g of salt as samples B and C. pH, colour and lycopene content of the test samples were found before and during preservation at a week-interval for 2 months in duplicates. The results showed that the initial MC of the fresh tomato / slurry and concentrate were 93.5 and 73.3%, respectively. Test sample pH before preservation was 4.22. Sample A recorded 18.79% decrease in pH while B and C had 9.2% and 54% increase in pH, respectively. Visual observation after 8th week of preservation showed that the tomato concentrate was still reddish but colour change (∆E) from the colorimeter revealed that sample A had the least value of 6.09 while B and C were 7.31 and 8.53, respectively. Initial lycopene concentration was 14.11 mg /100 g product. After preservation, Sample A had the least decrease (19.63%) compared to sample B (29.91% decrease) and sample C (33.3% decrease). Hence, common salt (12.0 g) and vegetable oil (30 ml) were able to maintain the acid content and minimize the reduction in lycopene content in the tomato concentrate.